I. Field of the Invention
The invention relates to a fuel injection device, particularly for an internal combustion engine, and to the method of controlling it.
II. Description of Related Art
Document FR 2 854 664 discloses an injection device comprising a tubular body in which a needle is mounted. The needle ends in a head that acts as a valve with a seat borne by the end of the tubular body. Pressurized fuel is fed into the tubular body and is halted by the valve. The needle has a longitudinal housing in which an electroactive material is positioned. When the electroactive material is excited, it lengthens, causing elastic lengthening of the needle and thus detaching the head from the seat. The valve is then open and the fuel passes between the seat and the head to be injected into a combustion chamber.
With an injector such as this, the response time for obtaining maximum valve lift is very short, typically less than 50 μs. It is therefore possible to control the extent to which the valve opens practically at every instance during the injection period. The instantaneous delivery of fuel and the formation form droplets are thus controlled.
However, it is necessary for the electroactive element to be in close proximity to the head. Now, because of the proximity to the combustion chamber, the electroactive element may be raised to temperatures that could be detrimental to its operation. In addition, installing it close to the tip of the injector may present problems of availability of space.